The present invention relates to a method of manufacturing a display apparatus using organic electroluminescence devices.
An organic electroluminescence (hereinafter referred to as EL) device utilizing the EL of an organic material comprises an organic layer sandwiched between an anode and a cathode. In the organic EL device with such a constitution, positive holes injected from the anode and electrons injected from the cathodes are recoupled with each other to emit light, which is taken out as emission light on the cathode or anode side. The organic EL device has drawn attention as a light-emitting device capable of emitting light at a high luminance of several hundred to several tens of thousand candelas per square meters under a low driving voltage of not more than 10 V. In addition, in the case of the organic EL devices, light-emitting devices for emitting light in each of different colors can be obtained by selecting the material of the organic layer, and, by arranging the light-emitting devices for emitting light in the individual colors in a predetermined condition, it is possible to constitute a display apparatus capable of multi-color display or full-color display.
Meanwhile, for enlarging the screen of the display apparatus using organic EL devices, there has been known a technology of constructing a single large display screen by joining a plurality of small-sized panels in a two-dimensional manner (see, for example, Japanese Patent Laid-open No. 2002-55634 (p. 5)). In this case, for realizing a high-definition display screen, it is required to reduce as much as possible the distance between the pixels at the joined portions (joints) so as to render the joints inconspicuous. Generally, however, it is difficult to form patterns such as pixel circuits, wirings, pixel electrodes and an organic film in an area ranging to end faces of the substrate.
In view of this, in a method of manufacturing a display apparatus by joining small-sized panels together, first, the patterns such as pixel circuits, wirings, pixel electrodes and an organic film are formed on a substrate larger than the small-sized panel for constituting the large screen, then the portions near the end faces for joining are cut with high accuracy by a substrate cutting apparatus such as a laser cutter and a dicing apparatus, and the small-sized panels thus obtained are arranged and joined to each other, thereby constituting a single large display screen.
In the case of constituting a single display screen (large screen) by joining together a plurality of small-sized panels as above-mentioned, however, it is necessary to make the distance between the pixles at the joints equal to the distance between the pixels at other portions, in order to render the joints between the panels as inconspicuous as possible. Therefore, the distance from a cut end face at an opening end of the display area to a pixel end is very short, so that the use of a substrate cutting apparatus such as a laser cutter and a dicing apparatus causes damage to the organic film portion in the display area.
In order to prevent this trouble, it is necessary to follow the procedure of cutting the substrate, provided with the pixel circuits, wirings and pixel electrodes, before the formation of the organic film to obtain the small-sized panel, thereafter forming the organic layer, a counter electrode and further a protective film on each small-sized panel, and then arranging the small-sized panels and joining them together. However, when such a procedure is followed, alignment marks normally arranged in the peripheral area are removed by the cutting of the substrate. Therefore, in the steps after the cutting of the substrate, it is impossible to position the substrate relative to a manufacturing apparatus with high accuracy. To obviate this problem, it is necessary to form the alignment marks in portions which are not removed by the cutting. In this case, however, it is necessary to prepare a special manufacturing apparatus, to modify the specifications of the manufacturing apparatuses, and so on, which causes a rise in manufacturing cost.